Scale inhibition

ABSTRACT

Phosphated hydroxy amines obtained by reacting polyphosphoric acid or phosphorus pentoxide with hydroxyamines, e.g., diethanolamine or triethanolamine, with or without neutralization, are used as scale inhibitors in brines, especially in oil wells, where calcium and barium salts are present.

United States Patent Inventors James R. Stanford;

Paul G. Vogelsang, Jr., both of Houston, Tex.

Appl. No. 857,239

Filed Sept. 11,1969

Patented Nov. 16, i971 Assignee Nalco Chemical Corporation Chicago, Ill. Continuation-impart of application Ser. No. 600,354, Dec. 9, 1966, now Patent No. 3,477,956. This application Sept. 11, 1969, Ser. No. 857,239

SCALE INHIBITION 17 Claims, No Drawings US. Cl 252/8.55 B,

[51] Int. Cl C02b 5/06, C09k 3/00 [50] Field of Search 252/180, 82, 389, 390, 8.55 B; 210/58; 21/2.7; 260/928,

5 6] References Cited UNITED STATES PATENTS 3,477,956 11/1969 Stanford et al. 252/855 Primary Examiner-Leon D. Rosdol Assistant Examiner-Irwin Gluck A110rneyJohnston, Root, O'Keeffe, Keil, Thompson and Shurtleff SCALE INHIBITION This application is a continuation-in-part of U.S. application Ser. No. 600,354, filed Dec. 9,1966, which has matured into U.S. Pat. No. 3,477,956.

BACKGROUND The invention is concerned with the prevention of scale deposits on solid surfaces in contact with hard water containing hardness scale-forming ions and with the preparation of compounds or compositions which are effective for this purpose. In particular, the invention is concerned with scale prevention in natural brines on ferrous metal walls and other solid surfaces, especially in oil producing and waterflood systems.

Inorganic polyphosphates have long been the most effective and economical sequestering agents used for the prevention of alkaline deposits in both oil producing and water flood systems. However, due to the problems encountered in feeding inorganic polyphosphates and their incompatibility with many waters, a need for a liquid organic phosphate with good solubility in waters containing hardness ions has become increasingly evident. For this reason, a liquid product with good solubility in produced waters and having the effectiveness and low treating cost of inorganic polyphosphates is needed.

OBJECTS One of the objects of the present invention is to provide new and improved compounds and compositions which will supply this need. Other objects will appear hereinafter.

INVENTION In accordance with the invention it has been found that phosphated hydroxy amines, with or without neutralization, are effective scale inhibitors in inhibiting scale deposits from water containing scale-forming chemicals and especially in inhibiting scale produced by natural brines, such as those found in underground formations, as, for example, in oil wells.

In the practice of the invention the phosphated hydroxy amine or a neutralization product thereof is introduced into hard water or brine which is usually contacted with metal or other solid surfaces while maintaining a hardness-ionprecipitation-preventing quantity in the order of 0.5 to 100 parts per million ppm. of the active efiective compound.

The products provided for the purpose of the invention can be described as polyphosphoric acid esters of hydroxy amines. They are preferably prepared by reacting the hydroxy amine with polyphosphoric acid and/or phosphorus pentoxide at elevated temperature, preferably in the order of about 50 C. to 175 C., although somewhat higher temperatures on the order of 200 C. to 250 C. can sometimes be used, depending upon the nature of the hydroxy amine reactant. In the early stages, the reaction is exothermic and care must be taken to control the temperature. The reaction time is preferably at least about 30 minutes. The reaction may be conducted for a longer period, however, e.g., up to 3 to 5 hours, to assure complete reaction. If desired, a catalyst, such as boron trifluoride etherate complex, may be used. When using polyphosphoric acid, the hydroxy amine can be added to the polyphosphoric acid liquid. Conversely, the phosphoric acid can be added to the hydroxy amine.

The resultant reaction product may be used as is, or it may be converted to a salt by partial to complete neutralization with an alkaline substance such as, for example, potassium or sodium hydroxide, potassium or sodium carbonate, ammonia, or a basic amino compound, e.g., tetramethyl ammonium hydroxide, methylamine, ethylamine, dicthylamine, triethanolamine, diethanolamine, triethyl amine, ethylene diamine, diethylene triamine, pyridine, morpholine or other amine. The amine should preferably be a water soluble amine or at least one that does not destroy solubility in water.

The hydroxy amines can be relatively simple amines, such as, diethanolamine or triethanolamine, or they can be more complex, such as, the still residues obtained in the manufacture of triethanolamine or the products obtained by oxyalkylating amines. They can be monoamines or polymines. They can have a single-hydroxy group as in aminoethylethanolamine but preferably have a plurality of hydroxy groups. The oxyalkylated amines are obtained by reacting an alkylene oxide, for example, ethylene oxide or l ,2- propylene oxide, with an amine containing one or more reactive hydrogen atoms. The preferred amines contain at least one 2-hydroxy ethyl group (-CH,CH,OH) provided by oxyethylation. The primary hydroxyl groups thereof are more effective than the secondary hydroxyl groups which would be provided by oxypropylation However, oxypropylation may be used if the oxypropylated product is then oxyethylated to provide terminal 2-hydroxyethyl groups. Ethylenediamine, for example, can be oxyethylated with four moles of ethylene oxide per mole of diamine to produce a diamine containing four 2-hydroxyethyl groups. By using both ethylene oxide and l,2-propylene oxide, products can be obtained with both hydroxyethyl and hydroxypropyl groups. The extent of the oxyalkylation can also be increased by increasing the number of moles of alkylene oxide and in some cases, it is desirable to use as many as 30 moles of alkylene oxide per mole of amine. In general, however, this is not necessary for the purpose of the invention. Other amines which can be oxyalkylated to provide hydroxy amines are diethylenetriamine, triethylenetetramine, tetraethylene pentamine, propylene diamine, dipropylcne triamine, and 1,6- hexane diamine. The amines usually employed for the purpose of the invention contain one to six nitrogen atoms and where the amines have alkylene groups connecting two or more nitrogen atoms such alkylene groups contain two to six carbon atoms. It is normally desirable that the hydroxy group which is to be phosphated should be separated from the nitrogen atom by at least one carbon atom and preferably by at least two carbon atoms as in the Z-hydroxyethyl group. Amines of this general structure are sometimes referred to as hydroxyalkyl amines or alkanolamines. It will be understood that mixtures of hydroxy amines as well as individual amines can be employed in preparing the phosphate esters. Hence, the products can consist of mixed phosphate esters and mixtures of phosphate esters of the hydroxy amines.

The resultant phosphate esters have an average of at least one and up to all of the hydroxyls of the amine replaced by phosphate ester groups derived from polyphosphoric acid or phosphorus pentoxide, said phosphate ester groups consisting essentially of one or both of a member selected from the group consisting of As previously indicated, the compounds provided by the invention include not only the free esters but also the salts of the esters derived by the partial to complete neutralization of the phosphate ester groups.

The invention will be further illustrated but is not limited by the following examples in which the quantities are stated in parts by weight unless otherwise indicated.

EXAMPLE I One hundred parts of a fully oxyethylated ethylenediamine made by reacting 4 moles of ethylene oxide with 1 mole of ethylenediamine was added to the reaction vessel and 25 parts of polyphosphoric acid was added gradually with agitation while allowing the temperature of the reaction mixture to increase to l00 C. The temperature was held at C. for 30 minutes. The reaction product was then cooled and 20 parts of N-propanol and 150 parts of water were added.

EXAMPLE [1 Fifty parts of polyphosphoric acid was added to 100 parts of 5 a triethanolamine residue (Amine N4) and the mixture was agitated with temperature control while allowing the temperature to increase to 100 C. The reaction mixture was then cooled and 150 parts of water added.

EXAMPLE 111 Four hundred parts of polyphosphoric acid was added to 250 parts of triethanolamine residue (Amine N-l) with agitation while allowing the temperature to increase to 105 C. The mixture was then heated to 130 C. and held at that temperature for 1 hour. It was then cooled and 250 parts of water added.

EXAMPLE 1V One hundred parts of polyphosphoric acid was added to 200 parts of aminoethylethanolamine which had previously been heated to 70 C. During the addition, the reaction mixture was agitated and the temperature was allowed to increase to 120 C. It was held at 120 C. for 30 minutes. then cooled and 600 parts of water added.

EXAMPLE V Two hundred parts of the product obtained in example 111 was mixed with 100 parts of 50 percent liquid caustic soda.

EXAMPLE V1 Four hundred parts of polyphosphoric acid was added to 250 parts of triethanolamine residue (Alkanolamine SB) in a reaction vessel with agitation and the temperature was allowed to increase to 200 C. The reaction mixture was then cooled and 250 parts of water added.

EXAMPLE Vll One hundred twenty-five parts of triethanolamine residue (Amine N-l) was mixed with 125 parts of a blend of 60 percent N.N'-diethanolethylenediamine and 40 percent N,N- tetraethanolethylenediamine and the mixture heated to 50 C. The mixture of amines was then added to 400 parts of polyphosphoric acid with agitation while allowing the temperature to increase to 150 C. The mixture was held at 150 C. for 30 minutes. then cooled below 100 C. and then 250 parts of water added.

EXAMPLE V111 Three hundred parts of the product obtained in example V11 was mixed at ambient temperature with 100 parts of 50 percent liquid caustic soda.

EXAMPLE 1X Four hundred parts of polyphosphoric acid was added to 300 parts of triethanolamine residue (Amine N-l) in a reaction vessel with agitation while allowing the temperature to rise to 140 C. The mixture was cooled below 100' C. and 300 parts of water added.

EXAMPLE X A mixture of 125 parts of triethanolamine residue (Alkanolamine SB) and 125 parts of triethanolamine residue (Amine NJ) was heated to 50 C. and 400 parts of polyphosphoric acid was slowly added with agitation while allowing the temperature to increase to 145 C. The resultant product was cooled to 100 C. and 250 parts of water added.

EXAMPLE X1 EXAMPLE X11 One hundred parts of the oxyethylated polyamine described in example X1 was neutralized with 50 parts of 99 percent acetic acid while keeping the temperature below about C. To this product was then added 350 parts of triethanolamine residue (Amine N-l Seven hundred parts of polyphosphoric acid was added to this mixture with agitation while allowing the temperature to increase to 130 C. The reaction mixture was held at this temperature for 1 hour, then cooled to C. and 300 parts of water added.

EXAMPLE X111 One hundred parts of the product of example Xll was mixed with 50 parts of 50 percent liquid caustic soda.

EXAMPLE XIV Four hundred parts of polyphosphoric acid was heated to 70 C. and 250 parts of triethanolamine residue (Amine N-l) was added with agitation while maintaining the temperature of the reaction mixture at -110 C. This temperature was maintained during three-fourths of the hydroxy amine addition and during the last one-fourth of said addition the tem perature was increased to 130 C. It was held at 130 C. for 30 minutes. The product was cooled to 95 C. and 250 parts of water added.

EXAMPLE XV One hundred twenty-five parts of triethanolamine residue (Alkanolamine SB) and parts of triethanolamine residue (Amine N-l) were blended with agitation while heating to 50 C. and the blend was added to 400 parts of polyphosphoric acid with agitation at a rate which allowed the temperature of the reaction mixture to increase to 150 C. The reaction mixture was held at 150 C. for 30 minutes, then cooled below 100 C. and 250 parts of water added.

EXAMPLE XVl Three hundred parts of triethanolamine residue (Amine N-l) and 100 parts of fully oxyethylated ethylenediamine (See example 1) were blended with agitation and heated to 50 C. The mixture of hydroxy amines was then added to 750 parts of polyphosphoric acid at 70 C. with agitation while allowing the temperature of the reaction mixture to increase to C. The temperature was held at 130 C. for 30 minutes. The product was cooled to below 100 C. and 700 parts of water added.

EXAMPLE XVII One hundred parts of the product of example XVl was mixed with 50 parts of liquid caustic soda.

EXAMPLE XVlll Three hundred parts of N,N'-tctraethanolethylcnediamine heated to 50 C. was added to 430 parts of polyphosphoric acid heated to 70 C. with agitation and the temperature of the mixture was allowed to increase to 130 C. It was held at 130 C. for 30 minutes, cooled to below 100 C. and 500 parts of water added.

EXAMPLE XlX The process was the same as in example XVlll except that 860 parts of polyphosphoric acid was employed and 800 parts of water was added.

EXAMPLE XX Three hundred parts of diethanolamine was added to 480 parts of polyphosphoric acid previously heated to 70 C. with agitation and the temperature of the reaction mixture was allowed to increase to 130 C. It was held at 130 C. for 30 minutes, then cooled below 100 C. and 500 parts of water added.

EXAMPLE XXl The procedure was the same as in example XX except that 960 parts of polyphosphoric acid was employed and 800 parts of water was added.

The phosphated hydroxy amines were evaluated as scale inhibitors in various amounts, heating the brine for a predetermined period and then determining the amount of calcium carbonate or calcium sulfate retained in solution.

A brine containing calcium carbonate was prepared by adding to distilled water 5,180 milligrams per liter (mg/l.) NaH- CO 22,200 mg./l. NaCl, 6 mg./1. Na SO 366 mg./l. MgCl, 61-1 0, and 2,000 mg./1. CaCl The water was sparged with carbon dioxide for 30 minutes before the salts were added and again for 30 minutes after the addition of the salts. This composition is hereinafter referred to as brine A.

To prepare a brine for testing against calcium sulfate, two separate brines were prepared. The first, brine B, was made by dissolving 7.5 grams of sodium chloride and 8.33 grams of calcium chloride in distilled water sufficient to make 1 liter. The second, brine C, was made by dissolving 7.5 grams of sodium chloride, plus 10.66 grams Na SO. in distilled water sufficient to make l liter. These two brines were then mixed in equal parts and the tests were carried out with the addition of various proportions of the chemicals to be tested. These tests were made at various temperatures over predetermined periods of time. The amount of calcium sulfate in solution was determined at the end of each test. Some tests were made under static conditions and others with agitation.

The following examples illustrate the results obtained.

EXAMPLE XXII In this test, brine A was used at a temperature of 130 F. for 20 hours in a static system, i.e., without agitation. The brine was seeded with 100 mg./l. of calcium carbonate.

A blank or control containing no added chemical had a calcium carbonate content of 1,800 mg./1. at the beginning of the test and retained only 540 mg./l. All of the calcium carbonate was retained by the addition of p.p.m. of the composition of example 111. Corresponding tests were made with other available commercial inhibitors and none of them caused the retention of all of the calcium carbonate at the same concentration.

EXAMPLE XXlll A test was carried out in the same manner as in example XXll with brine A except that the brine was not seeded with calcium carbonate. The control brine before heating contained 1,840 mg./l. After heating for hours at 130 F. it retained 680 mg./l. The addition of 5 p.p.m. and 10 p.p.m. of the composition of example 111 in both cases caused all of the calcium carbonate to be retained in solution.

The addition of 5 p.p.m. of the composition of example V caused 1,720 mg./l. of the calcium carbonate to be retained in solution. The addition of 10 p.p.m. of the same chemical caused all of the calcium carbonate to be retained in solution EXAMPLE XXIV The test was carried out with brine A in a static system at 160 F. for 20 hours using various concentrations of the scale inhibitors. The control before precipitation contained 1,800 mg./l. of calcium carbonate. After the test it contained 420 mg./l. of calcium carbonate. The compound of example 111 at 2.5 p.p.m. caused the retention of 1,020 mg./l. of calcium carbonate, at 5.0 p.p.m. 1,280 mg./l. of calcium carbonate, and at 10 p.p.m. 1,520 mg./l. ofcalcium carbonate.

EXAMPLE XXV The test was carried out in the same manner as in example XXIV except that the brine was seeded with 150 mg./l. of calcium carbonate. The amount of calcium carbonate retained in solution before precipitation was 1,760 mg./l. At the end of the test it contained 460 mg./l. The compositions of examples Ill and V were both tested at concentrations of 1 p.p.m., 2.5 p.p.m. 5 p.p.m. and 10 p.p.m. and were found to be effective in at least partially inhabiting calcium carbonate precipitation except at l p.p.m.

EXAMPLE XXVl The test was carried out using brine A at 200 F. for 20 hours in a static system. The brine was seeded with mg./l. of calcium carbonate.

The control before precipitation retained 1,760 mg./l. of calcium carbonate. After precipitation it retained 250 mg./l. of calcium carbonate. The compositions of examples 111 and V were both effective in causing a greater amount of calcium carbonate to be retained in solution at concentrations of 10 p.p.m. 20 p.p.m. and 30 p.p.m. At 30 p.p.m. the composition of example 111 caused all of the calcium carbonate to be retained in solution. At the same concentration, the compositions of example V caused 1,500 mg./l. of calcium carbonate to be retained in solution. Comparative tests of commercial scale inhibitors at the same concentration showed that they were less effective.

EXAMPLE XXVll The test was carried out using brine A at 160 F. for 20 hours in an unseeded static system. The control before precipitation retained 1,600 mg./l. of calcium carbonate. After the test it retained 480 mg./l. of calcium carbonate.

With the addition of 5 p.p.m. and 10 p.p.m. to separate samples of brine, the compound of example 111 caused the retention of 1,300 and 1,540 mg./l. of calcium carbonate, respectively. The composition of example Vl caused the retention of 600 mg./l. of calcium carbonate at a dosage of 5 p.p.m., and 1,320 mg./l. of calcium carbonate at a dosage of 10 p.p.m. The composition of example V11 caused the retention of 1,000 mg./l. of calcium carbonate at a dosage of 5 p.p.m., and 1,480 mg./l. of calcium carbonate at a dosage of 10 p.p.m. The composition of example lX caused the retention of 920 mg./l. of Calcium carbonate at a dosage of 5 p.p.m. and 1,440 mg./l. at a dosage of 10 p.p.m. The composition of example X caused the retention of 1,340 mg./l. of calcium carbonate at a dosage of 5 p.p.m., and 1,600 mg./l. of calcium carbonate at a dosage of 10 p.p.m. Thus, this composition was completely effective at 10 p.p.m. A commercial chemical caused the retention of S mg./l. of calcium carbonate at a dosage of 5 p.p.m. and 1,300 mg./1. of calcium carbonate at a dosage of 10 p.p.m.

EXAMPLE XXVlll The procedure was the same as in example XXVll except that the brine was seeded with mg./l. of calcium carbonate. The control before precipitation retained 1,800 mg./l. of calcium carbonate. After precipitation it retained 480 mg./l. of calcium carbonate.

The addition of 10 p.p.m. of the composition of example 111 caused the retention of 1,780 mg./l. of calcium carbonate. The addition of 10 p.p.m. of the composition of example V caused the retention of 1,560 mg./l. of calcium carbonate. The addition of 10 p.p.m. of the composition of example 1X caused the retention of 1,520 mg./l. of calcium carbonate. The addition of 10 p.p.m. of the composition of example X caused the retention of 1,760 mg./l. of calcium carbonate. A commercial chemical at a concentration of 10 p.p.m. caused the retention of 1,480 mg./l. of calcium carbonate.

EXAMPLE XXIX The test was carried out as described in example XXVlll. The control before precipitation retained 1,560 mg./l. of calcium carbonate. After the test it retained 340 mg./l. of calcium carbonate. At a dosage of 10 p.p.m. the composition of example lll caused the retention of 1,160 mg./l. of calcium carbonate. The composition of example X1 caused the retention of 480 mg./l. of calcium carbonate. The composition of example X11 caused the retention of 1,060 mg./l. of calcium carbonate. The composition of example Xlll caused the retention of 940 mg./l. of calcium carbonate. The composition of example XlV caused the retention of 1,280 mg./l. of calcium carbonate. The composition of example XV caused the retention of 1,320 mg./l. of calcium carbonate. The composition of example XVl caused the retention of 1,240 mg./l. of calcium carbonate. The composition of example XVll caused the retention of 1,200 mg./l. ofcalcium carbonate.

EXAMPLE XXX A mixture of 50 ml. of brine B and 50 ml. of brine C was used in these tests which were carried out at 160 F. for 30 hours in a static system. A control or blank before precipitation retained 3,200 mg./l. of calcium sulfate, calculated as calcium carbonate. After the test it retained 2,300 mgJl. The compositions of examples 111 and V at a dosage of l p.p.m. caused a retention of 3,100 and 3,000 mg./l., mg./l., respectively.

EXAMPLE XXXI The test was carried out as in example XXX except that the temperature was 212 F. for 6 hours with agitation. The control before precipitation retained 3,100 mg./l. of calcium sulfate, calculated as calcium carbonate. At the end of the test it retained 2,100 mg./l. The composition of example V at a dosage of 50 p.p.m. caused the retention of 2,900 mg./l., at a dosage of 100 p.p.m. 3,000 mg./l., at a dosage of 200 p.p.m. 3,100 mg./l.

EXAMPLE XXXll The test was carried out as in example XXXI except that the temperature was 250 F. and the time 20 hours. The control before precipitation retained 2,800 mg./l. of calcium sulfate, calculated as calcium carbonate, and 2,050 mg./l. of calcium sulfate was retained at the end of the test. The composition of example V at a dosage of 50 p,p.m. caused the retention of 2,600 mg./l. and at a dosage of 100 p.p.m. 2,800 mg./l.

EXAMPLE XXXlll The test conditions were the same as in example XXXll. Before precipitation the control retained 2,800 mg./l. of calcium sulfate, calculated as calcium carbonate. At the end of the test it retained 1,500 mg./l. of calcium sulfate. The composition of example V at.a dosage of 10 p.p.m. caused the retention of 2,800 mg./l. of calcium sulfate. Commercial scale inhibitors at the same dosages were less effective.

EXAMPLE XXXlV Test conditions were the same as in example XXX except that 100 ml. of brine B and 100 ml. of brine C were mixed together to form the test solution. The control before precipitation retained 3,000 mg./l. of calcium sulfate, calculated as calcium carbonate. At the end of the test, the control retained 2,075 mg./l. of calcium sulfate. At a dosage of 0.5 p.p.m. and l p.p.m. the compositions of examples Ill, Xll, Xlll, XIV, XV, XVI and XVll all completely inhibited precipitation of the calcium sulfate. The composition ofexample X1 caused 2,400 mg./l. of calcium sulfate to be retained at 0.5 p.p.m. and 2,900 mg./l. of calcium sulfate to be retained at 1 .m. 5 p p EXAMPLE XXXV One hundred seventy-five parts of polyphosphoric acid (8385 percent P was placed in a reaction vessel and heated to 50--60 C. With the heat off 70 parts of oxyethylated dipropylene triamine was slowly added over a period of 45 to 60 minutes while allowing the reaction mass temperature to increase to l25l30 C. This temperature was held by heating for 30 minutes. The product was cooled to below 100 C. and 200 parts of water added. This product was labeled Y-23l4.

The oxyethylated dipropylene triamine was prepared by reacting 417.5 parts of dipropylene triamine with 745 parts of ethylene oxide.

EXAMPLE XXXVI The procedure was the same as in example XXXV except that 225 parts of the polyphosphoric acid was used. The product was labeled Y--23 l 6.

25 EXAMPLE XXXVll The procedure was the same as in example XXXV except that 62.5 parts ofoxyethylated propylene diamine was used instead of the 70 parts of oxyethylated dipropylene triamine and this was prepared by reacting 4 pounds of ethylene oxide with 1.7",3b333s6fi3i65 'i555 diamineffhe product was labeled Y-2320.

EXAMPLE XXXVlll The procedure was the same as in example XXXVll except that 225 parts of the polyphosphoric acid was used. The product was labeled Y-2325.

EXAMPLE XXXlX The procedure was the same as in example XXXV except that 73 parts of oxyethylated hexamethylene diamine (1,6- hexane diamine) was used instead of the 70 parts of oxyethylated dipropylene triamine. The oxyethylated hexamethylene diamine was prepared by reacting 3.5 pounds of ethylene oxide with 1.65 pounds of hexamethylene diamine. The product was labeled Y-2338.

EXAMPLE XL The procedure was the same as in example XXXlX except that 225 parts of polyphosphoric acid was used (instead of 175 parts). The product was labeled Y-23 39.

EXAMPLE XLl TABLE 1 Calcium Carbonate Retained in Solution (as CaCO; rug/1.)

0.5 1.0 2.0 3.0 4.0 5.0 p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m.

Y-2314 l 2, 700 3, 300 3, 000 4, 000 4, 000 4,000 Y-2316 1 2, 600 2, 800 3, 600 3, 000 4, 000 4, 000 Y-2320 l 2, 600 3, 000 4, 000 4, 000 4, 000 4, 000 Y-2325 1 2, 600 2, 800 3, 900 4, 000 4, 000 4, 000 Y-2338 2 3, 700 4, 100 4, 200 4, .200 4, 200 4, .00 Y-2339 2 3, 000 4, 200 4, 200 4, 200 4, 200 4, 200

1 Blank nitor precipitation 2,600; Blank lltlOlt precipitation 4.000.

lll urk otter precipitntion 'l tltlt); Blank bnl'ot'u prvcipitntion 4,200.

These results show that the compositions of examples XXXV to XXXV!!! had some effect in inhibiting deposition of calcium carbonate at l p.p.m. some of them were completely effective at 2 or 3 p.p.m. and all were completely effective at 4 and 5 p.p.m. The compositions of examples XXXlX and XL were partially effective at 0.5 p.p.m. dosage, one of them was completely effective at l p.p.m. and both of them were effeciive at 2-5 p.p.m. dosage.

As previously mentioned, the hydroxy amine used in preparing the phosphate ester should preferably contain more than one hydroxyl group. For some unexplained reason, compounds made from amines containing more than one hydroxyl group, and especially those containing at least 2and up to 6 hydroxyl groups, are more effective and can be used at lower dosages. The amine can be a monoamine or a polyamine, i.e. contain two or more nitrogen atoms. As previously indicated, the hydroxyl group of the amine is separated from a nitrogen atom of the amine by at least one carbon atom, usually an alkylene group containing two to six carbon atoms, e.g., an alkylene group such as ethylene, propylene, butylene, and homologues. Where the hydroxyamine is derived by oxyalkylation of an amine up to oxyalkylene groups each containing two to four carbon atoms can be present in an oxyalkylene chain separating the terminal hydroxy ethyl group from a nitrogen atom. In such case, the oxyalkylene groups could be derived, for example, from ethylene oxide (oxyethylene), oxy l,2propylene oxide (oxypropylene) or oxy 1,2butylene oxide (oxybutylene) with the oxyalkylene groups in sequential order or in random arrangement (heteric). The hydroxy amine is preferably at least partially soluble in water and the end product is preferably soluble in water at the concentrations of use. While the dosage of the phosphate ester will normally be within the range of 0.5 to 100 p.p.m. certain types of uses may While the phosphate esters in the examples have been i prepared by using a commercial grade of polyphosphoric acid, also called 115 percent phosphoric acid", it will be unrequire higher dosages even as high as 200 to 500 p.p.m.

derstood that the reaction can also be carried out with phosphorus pentoxide or with a mixture of polyphosphoric acid and phosphorus pentoxide.

The compositions of the invention are especially effective in the inhibition of scaling on metal or other solid surfaces by calcium sulfate, barium sulfate, and calcium carbonate. They are useful in industry to prevent deposits of these scaleproducing compounds on metal surfaces of pumps, pipes, valves, tanks, and the like when waters containing the scaleproducing compounds (or precursors thereof, e.g., calcium bicarbonate) are treated in the concentrations aforesaid, i.e.,

0.5 to 100 parts per million. Places where scale buildup is most likely to become troublesome are those in the liquid handling systems wherein there is a change in fluid pressure, a change in fluid temperature, or a change in fluidflow rate.

The invention has utility in the prevention of similar scale deposits occurring in closed and once-through cooling systems where hard water is employed.

The compounds also have utility in boiler feedwaters and in waters charged to certain desalinization equipment where- 4 fonnation which has a high calcium content water. As the waters reach the producing well they mix, and a calcium sulfate deposition occurs, either in the formation at the well bore or in the producing equipment. This requires the removal of the tubing, rods and pump for cleaning, and a fracturing job it the formation is plugged, which is the case most of the time.

By the practice of the present invention the formation of scale in the producing equipment and underground formation can be reduced or prevented.

Similarly, the invention is applicable to the treatment of water supply wells. The phosphate esters can also be added directly to the input well of a waterflood system consisting or one or more input wells and one or more producing wells.

We claim:

1. A process for preventing scale deposits from the class consisting of barium sulfate, calcium sulfate, calcium carbonate and mixtures thereof from water containing said scaleforming chemicals which comprises adding to said water an effective scale inhibiting amount of a phosphate ester of a hydroxy amine in which the hydroxyl groups of the amine are separated from a nitrogen atom of the amine by at least one carbon atom and the phosphate ester groups consist essentially of one or both of a member selected from the group consisting of least partially in the form of a salt thereof.

5. A process as claimed in claim 1 wherein said water is a natural hard water or brine.

6. A process as claimed in claim 1 in which said water is a cooling water.

7. A process as claimed in claim 1 in which said water is a boiler feed water.

8. A process as claimed in claim 1 in which said water is a disposal water.

9. A process as claimed in claim 1 in which said water is in an underground oil-producing fonnation.

10. A process as claimed in claim 1 in which said phosphate ester is added to water used in a water flood system to increase the production of oil wells.

11. A process as claimed in claim 1 in which said hydroxy amine contains two to six nitrogen atoms connected by alkylene groups containing two to six carbon atoms.

12. A process as claimed in claim 1 in which said hydroxy amine is a diamine having the amino nitrogen atoms connected by an alkylene chain of two to six carbon atoms.

13. A process as claimed in claim 12 in which said diamine is oxyethylated propylene diamine.

14. A process as claimed in claim 12 in which said diamine is oxyethylated hexamethylene diamine.

15. A process as claimed in claim 1 in which said hydroxyamine is an oxyalkylated dipropylene triamine containing not more than 30 moles of two to four carbon alkylene oxide per mole of amine and having a terminal 2-hydroxyethyl group.

16. A process as claimed in claim 1 in which said hydroxyamine is an oxyalkylated propylene diamine containing not more than 30 moles of two to four carbon alkylene oxide per mole of amine and having a terminal 2-hydroxyethyl group.

17. A process as claimed in claim 1 in which said hydroxyamine is an oxyalkylated hexamethylene diamine containing not more than 30 moles of two to four carbon alkylene oxide per mole of amine and having a terminal 2-hydroxyethyl group.

PWW UNETEB STATES FA'EENT (5/69) e Q CERTEFFQKTE GE CORRE THEN Patent No. 3,620,974 Dated November 16, 1971 Inventofls) James R. Stanford and Paul G. Vogelsang Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

First page, left-hand column, line 13, insert The portion of the term of the patent subsequent to Nov. 11, 1986, has been disclaimed.

Column 1, line 45, "p.p.m." should read (p.p.m.)

Column 6, line 21, irmabiting should read inhibiting Column 9, line 5, "l p.p.m. should read l p.p.m.,

Signed and sealed this 23rd day of I E-Ly i972. 

2. A process as claimed in claim 1 in which said hydroxy amine contains one to six amino nitrogen atoms and not more than Six hydroxyl groups.
 3. A process as claimed in claim 1 wherein said amount is 0.5 to 100 parts per million parts of said water.
 4. A process as claimed in claim 1 in which said ester is at least partially in the form of a salt thereof.
 5. A process as claimed in claim 1 wherein said water is a natural hard water or brine.
 6. A process as claimed in claim 1 in which said water is a cooling water.
 7. A process as claimed in claim 1 in which said water is a boiler feed water.
 8. A process as claimed in claim 1 in which said water is a disposal water.
 9. A process as claimed in claim 1 in which said water is in an underground oil-producing formation.
 10. A process as claimed in claim 1 in which said phosphate ester is added to water used in a water flood system to increase the production of oil wells.
 11. A process as claimed in claim 1 in which said hydroxy amine contains two to six nitrogen atoms connected by alkylene groups containing two to six carbon atoms.
 12. A process as claimed in claim 1 in which said hydroxy amine is a diamine having the amino nitrogen atoms connected by an alkylene chain of two to six carbon atoms.
 13. A process as claimed in claim 12 in which said diamine is oxyethylated propylene diamine.
 14. A process as claimed in claim 12 in which said diamine is oxyethylated hexamethylene diamine.
 15. A process as claimed in claim 1 in which said hydroxyamine is an oxyalkylated dipropylene triamine containing not more than 30 moles of two to four carbon alkylene oxide per mole of amine and having a terminal 2-hydroxyethyl group.
 16. A process as claimed in claim 1 in which said hydroxyamine is an oxyalkylated propylene diamine containing not more than 30 moles of two to four carbon alkylene oxide per mole of amine and having a terminal 2-hydroxyethyl group.
 17. A process as claimed in claim 1 in which said hydroxyamine is an oxyalkylated hexamethylene diamine containing not more than 30 moles of two to four carbon alkylene oxide per mole of amine and having a terminal 2-hydroxyethyl group. 